A strange thing has happened to me over the two years since I moved to Wales. I have become susceptible to a novel and disturbing sensation: pride in my adopted country. England, the land of my birth, means nothing to me, nor does Britain. I despise nationalism. But I have been overtaken by an irrational impulse. I find myself supporting Wales in rugby, football (someone's got to, and we did beat Liechtenstein) and all its competing claims against other nations.

This impulse arises from a number of observations: in two years of walking through the valleys and over the hills here, I have never been shouted at; the cafe in the local leisure centre serves smoothies in measures labelled "small" (about a pint) and "regular" (about two pints); when I wrote to a very active councillor asking his permission to recommend him for a gong, he replied: "I would prefer not to seek such an honour."

Through such observations, I have begun to form the impression that Wales is less socially stratified, less grasping, more liberal than the rest of Britain. Though I am an outsider, from the colonial power, with an unerring ability to wind people up, I have never been made to feel unwelcome. And it seldom rains here, and then only at night. (That's not strictly true, but this is what nationalism does.)

In this spirit I have to record that something is missing. Its absence offends my newfound national pride. It mocks our attempt to become a coherent country. It means that the Gogs (of north Wales) and the Hwntws (of south Wales) will for ever be at each other's throats. It means that the greenest nation in the UK is locked into unsustainability. It is also bleeding ridiculous. As far as I can discover, this is the only country in Europe that you cannot traverse by train without spending most of the journey passing through another. The only rail link that allows you to travel from north to south crosses the border near Llangollen and doesn't re-enter Wales until it approaches Abergavenny, 100 miles away.

The railway map of Wales is a classic indicator of an extractive economy. The lines extend either towards London or towards the ports. As Eduardo Galeano established in The Open Veins of Latin America, the infrastructure of a country is a guide to the purpose of its development. If the main roads and railways form a network, linking the regions and the settlements within the regions, they are likely to have been developed to enhance internal commerce and mobility. If they resemble a series of drainage basins, flowing towards the ports and borders, they are likely to have been built to empty the nation of its wealth for the benefit of another. Like Latin America, Wales is poor because it was so rich. Its abundant natural resources gave rise to an extractive system, designed to leave as little wealth behind as possible.

Just as the railway network was developed largely for the benefit of another economy, it was dismantled for the same purpose. Wales was hit very hard by the Beeching cuts of the 1960s. Before that, one of the lines that could have been used as part of a north-south railway was flooded by Llyn Celyn, a reservoir that drowned the village of Capel Celyn in order to supply water to Liverpool. It was this act of enclosure that inspired RS Thomas's famous poem Reservoirs, in which he mourned "... the smashed faces / Of the farms with the stone trickle / Of their tears down the hills' side". The dam wall was built across the Bala-to-Ffestiniog line.

Before Beeching, a handful of minor routes existed that could have enabled a determined passenger who was prepared to make a few changes to travel from north to south, but there was no line either conceived or used as a long-distance railway connecting the nation. Could such a railway be built? Thanks to the efforts of a remarkable man, the idea is beginning to seep into the national consciousness.

Archimandrite Deiniol is the only Orthodox priest serving in north Wales. Bull-headed, magnificently bearded, he is the spokesman for Yn Ein Blaenau, a group set up to lobby for the regeneration of Blaenau Ffestiniog, one of the country's poorest communities. Unlike many other depressed Welsh towns, Blaenau has a way out: but it is blocked. It is surrounded - hideously - by the waste from its slate workings. The British government has a policy of replacing virgin building stone with mining spoil and rubble. The slate waste around Blaenau would supply Britain with roadstone for years, but it's stuck there until the Conwy Valley railway line is upgraded. Deiniol has been negotiating with the byzantine network of railway companies, authorities and regulators, and has so far been frustrated.

But in doing so, he has learned a good deal about how the railways of the UK work - or don't. He has also discovered that a railway can be critical to a region's regeneration, and that the north-south roads in Wales are close to gridlock.

There are plenty of lobbyists calling for new roads, but Deiniol's plan is likely to be cheaper and more sustainable. His survey of the disused railway lines of Wales shows that there is one route - from Rhyl through Denbigh, Rhuthun, Corwen, Newtown, Llanidloes, Rhaeadr and Builth Road to Dowlais - that would require only two miles of new formation to link Holyhead to Cardiff. The rest of the way makes use of current and former railways. He proposes that short feeder lines also be built, connecting this trunk route to Mold, Llangollen, Oswestry, Bala, Hay-on-Wye and Brecon.

The One-Wales Line could not only offer a much faster journey than the current long detour through England, but it would also knit the other railways of Wales into a coherent network, as it crosses the north coast railway, the Cambrian line and the Shrewsbury-to-Swansea line. It would help to regenerate a desperately poor region in the south called the Heads of the Valleys. The project would look rather like the Western Railway Corridor in Ireland, which is reopening 184km of disused lines between Limerick and Sligo.

The least the Welsh assembly government should do is to commission a feasibility study and cost-benefit analysis of Deiniol's plan. His railway would help Wales looks like a country again, rather than a depot for someone else's empire.